1. Field of the Invention
The present invention relates to systems and methods for transmitting data, and in particular to a system and method for equalizing digital data signals.
This Application is also related to the following:
application Ser. No. 11/653,517, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Jan. 16, 2007, by Ernest C. Chen, which is a continuation of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/165,710, entitled “SATELLITE TWTA ON-LINE NON-LINEARITY MEASUREMENT”, filed on Jun. 7, 2002, by Ernest C. Chen, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/236,414, entitled “SIGNAL, INTERFERENCE AND NOISE POWER MEASUREMENT”, filed on Sep. 6, 2002, by Ernest C. Chen and Chinh Tran, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/693,135, entitled “LAYERED MODULATION FOR ATSC APPLICATIONS”, filed on Oct. 24, 2003, by Ernest C. Chen, which claims benefit to Provisional Patent Application No. 60/421,327, filed Oct. 25, 2002 and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/913,927, entitled “CARRIER TO NOISE RATIO ESTIMATIONS FROM A RECEIVED SIGNAL”, filed on Aug. 5, 2004, by Ernest C. Chen, which is a continuation in part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 11/619,173, entitled “PREPROCESSING SIGNAL LAYERS IN LAYERED MODULATION DIGITAL SIGNAL SYSTEM TO USE LEGACY RECEIVERS”, filed Jan. 2, 2007, which is a continuation of application Ser. No. 10/068,039, entitled “PREPROCESSING SIGNAL LAYERS IN LAYERED MODULATION DIGITAL SIGNAL SYSTEM TO USE LEGACY RECEIVERS”, filed on Feb. 5, 2002, by Ernest C. Chen, Tiffany S. Furuya, Philip R. Hilmes, and Joseph Santorn now issued as U.S. Pat. No. 7,245,671, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/693,421, entitled “FAST ACQUISITION OF TIMING AND CARRIER FREQUENCY FROM RECEIVED SIGNAL”, filed on Oct. 24, 2003, by Ernest C. Chen, now issued as U.S. Pat. No. 7,151,807, which claims priority to Provisional Patent application Ser. No. 60/421,292, filed Oct. 25, 2002, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 11/603,776, entitled “DUAL LAYER SIGNAL PROCESSING IN A LAYERED MODULATION DIGITAL SIGNAL SYSTEM”, filed on Nov. 22, 2006, by Ernest C. Chen, Tiffany S. Furuya, Philip R. Hilmes, and Joseph Santoru, which is a continuation of application Ser. No. 10/068,047, entitled “DUAL LAYER SIGNAL PROCESSING IN A LAYERED MODULATION DIGITAL SIGNAL SYSTEM”, filed on Feb. 5, 2002, by Ernest C. Chen, Tiffany S. Furuya, Philip R. Hilmes, and Joseph Santom, now issued as U.S. Pat. No. 7,173,981, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/962,346, entitled “COHERENT AVERAGING FOR MEASURING TRAVELING WAVE TUBE AMPLIFIER NONLINEARITY”, filed on Oct. 8, 2004, by Ernest C. Chen, which claims priority to Provisional Patent Application Ser. No. 60/510,368, filed Oct. 10, 2003, and which is a continuation-in-part of Application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 11/655,001, entitled “AN OPTIMIZATION TECHNIQUE FOR LAYERED MODULATION”, filed on Jan. 18, 2007, by Weizheng W. Wang, Guancai Zhou, Tung-Sheng Lin, Ernest C. Chen, Joseph Santoru, and William Lindsey, which claims priority to Provisional Patent Application No. 60/421,293, filed Oct. 25, 2002, and which is a continuation of application Ser. No. 10/693,140, entitled “OPTIMIZATION TECHNIQUE FOR LAYERED MODULATION”, filed on Oct. 24, 2003, by Weizheng W. Wang, Guancai Zhou, Tung-Sheng Lin, Ernest C. Chen, Joseph Santoru, and William Lindsey, now issued as U.S. Pat. No. 7,184,489, which is a continuation-in-part of application Ser. No. 09/844, 401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 11/656,662, entitled “EQUALIZERS FOR LAYERED MODULATION AND OTHER SIGNALS”, filed on Jan. 22, 2007, by Ernest C. Chen, Tung Sheng Tin, Weizheng W. Wang, and William C. Lindsey, which claims priority to Provisional Patent Application No. 60/421,241, filed Oct. 25, 2002, and which is a continuation of application Ser. No. 10/691,133, entitled “EQUALIZERS FOR LAYERED MODULATED AND OTHER SIGNALS”, filed on Oct. 22, 2003, by Ernest C. Chen, Tung-Sheng Tin, Weizheng W. Wang, and William C. Lindsey, now issued as U.S. Pat. No. 7,184,473, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/961,579, entitled “EQUALIZATION FOR TWTA NONLINEARITY MEASUREMENT” filed on Oct. 8, 2004, by Ernest C. Chen, which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/532,632, entitled “LOWER COMPLEXITY LAYERED MODULATION SIGNAL PROCESSOR”, filed on Apr. 25, 2005, by Ernest C. Chen, Weizheng W. Wang, Tung-Sheng Tin, Guangcai Zhou, and Joseph Santorn, which is a National Stage Application of PCT US03/32264, filed Oct. 10, 2003, which claims priority to Provisional Patent Application No. 60/421,331, entitled “LOWER COMPLEXITY LAYERED MODULATION SIGNAL PROCESSOR”, filed Oct. 25, 2002, by Ernest C. Chen, Weizheng W. Wang, Tung-Sheng Tin, Guangcai Zhou, and Joseph Santorn, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/532,631, entitled “FEEDER LINK CONFIGURATIONS TO SUPPORT LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 25, 2005, by Paul R. Anderson, Joseph Santorn and Ernest C. Chen, which is a National Phase Application of PCT US03/33255, filed Oct. 20, 2003, which claims priority to Provisional Patent Application No. 60/421,328, entitled “FEEDER LINK CONFIGURATIONS TO SUPPORT LAYERED MODULATION FOR DIGITAL SIGNALS”, filed Oct. 25, 2002, by Paul R. Anderson, Joseph Santoru and Ernest C. Chen, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/532,619, entitled “MAXIMIZING POWER AND SPECTRAL EFFICIENCIES FOR LAYERED AND CONVENTIONAL MODULATIONS”, filed on Apr. 25, 2005, by Ernest C. Chen, which is a National Phase Application of PCT Application US03/32800, filed Oct. 16, 2003, which claims priority to Provisional Patent Application No. 60/421,288, entitled “MAXIMIZING POWER AND SPECTRAL EFFICIENCIES FOR LAYERED AND CONVENTIONAL MODULATION”, filed Oct. 25, 2002, by Ernest C. Chen and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/532,524, entitled “AMPLITUDE AND PHASE MATCHING FOR LAYERED MODULATION RECEPTION”, filed on Apr. 25, 2005, by Ernest C. Chen, Jeng-Hong Chen, Kenneth Shum, and Joungheon Oh, which is a National Phase Application of PCT Application US03/31199, filed Oct. 3, 2003, which claims priority to Provisional Patent Application No. 60/421,332, entitled “AMPLITUDE AND PHASE MATCHING FOR LAYERED MODULATION RECEPTION”, filed Oct. 25, 2002, by Ernest C. Chen, Jeng-Hong Chen, Kenneth Shurn, and Joungheon Oh, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524, and also claims priority to;
application Ser. No. 10/532,582, entitled “METHOD AND APPARATUS FOR TAILORING CARRIER POWER REQUIREMENTS ACCORDING TO AVAILABILITY IN LAYERED MODULATION SYSTEMS”, filed on Apr. 25, 2005, by Ernest C. Chen, Paul R. Anderson and Joseph Santorn, now issued as U.S. Pat. No. 7,173,977, which is a National Stage Application of PCT Application US03/32751, filed Oct. 15, 2003, which claims priority to Provisional Patent Application No. 60/421,333, entitled “METHOD AND APPARATUS FOR TAILORING CARRIER POWER REQUIREMENTS ACCORDING TO AVAILABILITY IN LAYERED MODULATION SYSTEMS”, filed Oct. 25, 2002, by Ernest C. Chen, Paul R. Anderson and Joseph Santorn, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/532,509, entitled “ESTIMATING THE OPERATING POINT ON A NONLINEAR TRAVELING WAVE TUBE AMPLIFIER”, filed on Apr. 25, 2005, by Ernest C. Chen and Sham Maitra, now issued as U.S. Pat. No. 7,230,480, which is a National Stage Application of PCT Application US03/33130 filed Oct. 17, 2003, and which claims priority to Provisional Patent Application No. 60/421,289, entitled “ESTIMATING THE OPERATING POINT ON A NONLINEAR TRAVELING WAVE TUBE AMPLIFIER”, filed Oct. 25, 2002, by Ernest C. Chen and Shamik Maitra, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/519,322, entitled “IMPROVING HIERARCHICAL 8PSK PERFORMANCE”, filed on Dec. 23, 2004 by Ernest C. Chen and Joseph Santoru, which is a National Stage Application of PCT US03/020,862 filed Jul. 1, 2003, which claims priority to Provisional Patent Application No. 60/392,861, filed Jul. 1, 2002 and Provisional Patent Application No. 60/392,860, filed Jul. 1, 2002, and which is also related to application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/519,375, entitled “METHOD AND APPARATUS FOR LAYERED MODULATION”, filed on Jul. 3, 2003, by Ernest C. Chen and Joseph Santoru, which is a National Stage Application of PCT US03/20847, filed Jul. 3, 2003, which claims priority to Provisional Patent Application No. 60/393,437 filed Jul. 3, 2002, and which is related to Application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524;
application Ser. No. 10/692,539, entitled “ON-LINE PHASE NOISE MEASUREMENT FOR LAYERED MODULATION”, filed Oct. 24, 2003, by Ernest C. Chen, which claims priority from Provisional Patent Application No. 60/421,291, filed Oct. 25, 2002, entitled “ON-LINE PHASE NOISE MEASUREMENT FOR LAYERED MODULATION”; and
application Ser. No. 10/692,491, entitled “ONLINE OUTPUT MULTIPLEXER FILTER MEASUREMENT”, filed on Oct. 24, 2003, by Ernest C. Chen, which claims priority to Provisional Patent Application No. 60/421,290, filed Oct. 25, 2002, and which is a continuation-in-part of application Ser. No. 09/844,401, entitled “LAYERED MODULATION FOR DIGITAL SIGNALS”, filed on Apr. 27, 2001, by Ernest C. Chen, now issued as U.S. Pat. No. 7,209,524.
2. Description of the Related Art
Digital signal communication systems have been used in various fields, including digital TV signal transmission, both terrestrial and satellite. As the various digital signal communication systems and services evolve, there is a burgeoning demand for increased data throughput and added services. However, it is more difficult to implement improvement in old systems and new services when it is necessary to replace existing legacy hardware, such as transmitters and receivers. New systems and services are at an advantage when they can utilize existing legacy hardware. In the realm of wireless communications, this principle is further highlighted by the limited availability of electromagnetic spectrum. Thus, it is not possible (or at least not practical) to merely transmit enhanced or additional data at a new frequency.
The conventional method of increasing spectral capacity is to move to a higher-order modulation, such as from quadrature phase shift keying (QPSK) to eight phase shift keying (8PSK) or sixteen quadrature amplitude modulation (16QAM). Unfortunately, QPSK receivers cannot demodulate conventional 8PSK or 16QAM signals. As a result, legacy customers with QPSK receivers must upgrade their receivers in order to continue to receive any signals transmitted utilizing 8PSK or 16QAM modulation.
It is advantageous for systems and methods of transmitting signals to accommodate enhanced and increased data throughput without requiring additional frequency. It is also advantageous for enhanced and increased throughput signals for new receivers to be backwards compatible with legacy receivers. There is further advantage for systems and methods which allow transmission signals to be upgraded from a source separate from the legacy transmitter.
It has been proposed that a layered modulation signal, transmitting non-coherently upper as well as lower layer signals be employed to meet these needs. Such layered modulation systems allow for higher information throughput with backwards compatibility. However, even when backward compatibility is not required (such as with an entirely new system), layered modulation can still be advantageous because it requires a TWTA peak power significantly lower than that for a conventional 8PSK or 16QAM modulation formats for a given throughput.
Equalizers are widely used in communication systems, and are particularly useful when there are multipath and/or other distortion effects in the transmission channel. Equalizers can also be used to cancel “echo” in the system. However, such equalizers typically require apriori knowledge of the channel impulse response, or knowledge of a pre-determined training sequence that is transmitted in the channel. Since the training sequence is known, the channel impulse response can be determined from the training sequence and appropriately equalized. Blind equalizers, which do not have apriori knowledge of the channel impulse response or knowledge of the pre-determined training sequence, are known, but such equalizers typically exhibit poor performance.
Accordingly, there is a need for systems and methods for accurately equalizing communication channels that does not require apriori knowledge of the channel impulse response or a training sequence. The present invention meets this need and provides further advantages as detailed hereafter.